1. The Field of the Invention
The present invention relates to distributed service activation technology; and more specifically, to mechanisms for providing continuity in session state when service module recycling is requested during the session.
2. Background and Related Art
Computing technology has transformed the way we work and play. Computing systems now take a wide variety of forms including desktop computers, laptop computers, tablet PCs, Personal Digital Assistants (PDAs), household devices and the like. In its most basic form, a computing system includes system memory and one or more processors. Software in the system memory may be executed by the processor to direct the other hardware of the computing system to perform desired functions.
Distributed computing technology permits multiple applications or processes to communicate to accomplish a particular task. Such distributed computing need not be physically distributed. For instance, objects within the same process may communicate, and objects in different processes may communicate on the same local computing system. On the other hand, distributed computing technology may also permit communication between processes running on remote computing systems. Distributed computing technologies enable computing systems to communicate whether locally, or even over vast distances, thereby expanding on computer functionality.
In a distributed computing environment, a service module often responds to messages originating from one or more other requesting modules, whether or not the requesting and service modules are located on the same physical machine, or are remotely located. In order to provide the service, the service module sometimes engages in an entire session with the other computing system. Sessions are characterized by a number of message exchanges in which there is state regarding the session that should be maintained between sessions in order for the session to be successfully completed.
One conventional problem with such session-oriented message exchanges occurs when the service module is recycled. Recycling refers to the de-activation of one instance of the service module. Future request to the service module are handled by another instance of the service module. Such recycling should ideally be transparent from the viewpoint of the request module(s). During a session-oriented message exchange, a service module will typically access incoming messages via an input buffer. Some input buffers are configured such that when an instance of the service module is determined to be recycled, the service module instance may no longer access the input buffer.
If not all of the session messages had yet been provided to the input buffer, all future session messages would be received by another instance of the service module. Session state is often maintained in volatile memory. Accordingly, the second instance of the service module may not have access to the same session state that the first instance of the service module did. Thus, the session is less likely to be successfully competed by the second instance of the service module. Session state may be preserved in a non-volatile memory during recycling. However, access to non-volatile memory is slower than access to volatile memory most typically by orders of magnitude.
Therefore, what would be advantageous is a mechanism for preserving session state for a service module even should a recycle determination for the service module instance that handles the session occur mid-session.